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Plasticity in the myenteric plexus of the rat ileum after long‐term sympathectomy
Author(s) -
Milner P.,
Lincoln J.,
Belai A.,
Burnstock G.
Publication year - 1995
Publication title -
international journal of developmental neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.761
H-Index - 88
eISSN - 1873-474X
pISSN - 0736-5748
DOI - 10.1016/0736-5748(95)00028-f
Subject(s) - sympathectomy , guanethidine , medicine , endocrinology , myenteric plexus , neuropeptide y receptor , ileum , vasoactive intestinal peptide , calcitonin gene related peptide , substance p , neuropeptide , immunohistochemistry , receptor , stimulation
To investigate the effect of chronic sympathectomy on the innervation of a tissue with an extensive intrinsic component, 1‐week‐old rat pups were treated with 50 mg/kg guanethidine for 3 weeks, a treatment shown to produce complete and long‐lasting sympathectomy, and the ileum examined. Changes in the levels of noradrenaline, neuropeptide Y, calcitonin gene‐related peptide, substance P and vasoactive intestinal polypeptide in the external muscle layers containing the myenteric plexus of the ileum were determined between 6 and 20 weeks of age. After sympathectomy, noradrenaline levels were initially depleted (3% of age‐matched controls at 6 weeks, P <0.001, and 18% of age‐matched controls at 12 weeks, P <0.001), but were not significantly reduced at 20 weeks (67% of age‐matched controls). Such increases in noradrenaline content with time after sympathectomy did not occur in the mesenteric vein (levels in 20‐week‐old sympathectomized rats were 2% of the control values ( P <0.001). In the myenteric plexus, catecholamine fluorescent nerve fibres were seen in the 12‐week‐old sympathectomized rats, although tyrosine hydroxylase‐immunoreactivity was absent. Guanethidine sympathectomy had no effect on the neuropeptide levels in 6‐week‐old rat ileum but there was a selective increase at 20 weeks; the levels of calcitonin gene‐related peptide and substance P were increased (×3, P <0.001 and ×1.6, P <0.05, respectively) while vasoactive intestinal polypeptide and neuropeptide Y levels were unchanged. Short‐term sympathectomy (destruction of sympathetic nerve terminals by acute 6‐hydroxydopamine treatment) had no effect on noradrenaline or peptide levels in this tissue. The changes in innervation noted after long‐term sympathectomy may represent a part of the adaptive response of the enteric nervous system which permits normal intestinal function in the absence of extrinsic neuronal inputs.